# Finding Centers of Rotation: Sentence Starters and Frames

Some ideas for sentence frames/starters that could be incorporated into your lesson are listed below.  If you think a sentence frame/starter will be helpful, consider how will it support students’ mathematical learning and/or development of academic language, and decide which sentence frame/starter (from the list below or that you create) would best support students’ learning. You may find that the starters and frames vary in level of difficulty, and plan to provide them to students accordingly.

## Starters

To rotate the line segment AB around a center of rotation C, I ____________________________________________________________________________________________________________

I noticed that when a line segment rotates around a center of rotation, the endpoints of the line segment

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

I predict that if I rotate a triangle around a center of rotation, the vertices of the triangle will

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

I know that the center of rotation for the two line segments in part 4 (a/b/c/d) must

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

## Frames

I noticed that when a line segment rotates around a center of rotation, the _______________of the line segment remain the same

distance away from the center of rotation.

I think that the center of rotation for these two line segments in part 4 is probably _____________________________________

because__________________________________________________________________________________________________

## *****************************************************************************

Students should have opportunities to see, hear, and write key mathematical ideas during this activity. There are some specific terms that students need to understand in order to engage in this task, and there are some additional terms and phrases that may surface as the students engage with the task. You may think of additional words or phrases that are key to this activity.  As the task is introduced, solved by the students, and discussed, ensure that students have opportunities to experience (i.e., through discussion, pictures, and the use of gestures) and to build understanding for key words and phrases. Examples of words and phrases that may be involved in work on this problem include:

• rotate; rotation; rotated; center of rotation
• line segment
• path; locations
• endpoint; midpoint
• circle
• orientation
• distance from the center of rotation is constant
• congruent
• perpendicular bisector
• point that is equidistant from both line segments
• angle of rotation